PC ATX Power Supply; Are These Filter Capacitors and how significant are they?

Discussion in 'General Electronics Chat' started by Chrisoborski, Sep 18, 2010.

  1. Chrisoborski

    Thread Starter Member

    Oct 12, 2009
    25
    0
    I've got an idea....

    I've got a industrial/office power strip that has 9 sockets. I Record and edit Audio on my computer and i've read articles about proper grounding and noise suppression power strips.

    I've got a bunch of old PC power supply's, ATX also. Located on the inside and directly connected to the two terminals on the female ATX socket is a blue Capacitor going across each terminal, and also in parallel with this is a small resistor. I haven't checked the value of the resistor yet. And i can't read the funny codes on these box shaped capacitors. I've got two PC power supply's that i took these from so there is two caps 1 each for each power Supply. I uploaded pics below.
    ---[::EDIT::]
    Basically i'll sum it up.... What are they filtering and are these any use by adding to my powerstrip?
    ---[::END::]

    Questions::-
    I am wondering What these two components are actually doing?
    Can someone tell me the values of the caps or how i would calculate the value?
    Could possible use them to filter "noise" on my power strip i mentioned?
    Maybe i could Use these instead of buying an expensive power strip that filters noise ... ??


    I was thinking this could be a easy project if it does anything. Of course it doesn't help the ground though.
    Any help would be Great.
    Cool!! [​IMG]
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    Last edited: Sep 18, 2010
  2. tom66

    Senior Member

    May 9, 2009
    2,613
    214
    I think they are legally required for EMI supression.

    They will have little use on a power strip for reducing noise that exists on the line already.

    Besides, you will find most noise on the power supply output is internally generated.
     
  3. Chrisoborski

    Thread Starter Member

    Oct 12, 2009
    25
    0
    Okay, Thought i'd see anyway.
     
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    you will need an LC circuit to suppress AC mains noise that generated from SMPS and the likes.

    What you have are two 0.33uF caps rated at 250VAC. which used for noise suppression together with inductors. Commonly known as line filter
     
  5. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    I don't regard messing with the mains supply as a

    'cool easy project'

    Take care with modifying the mains, even if you are using 250 volt caps in America.
     
  6. sceadwian

    New Member

    Jun 1, 2009
    499
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    EMI and probably power factor correction as well.

    There's nothing really to decode on the caps, it's all listed in black/blue and white.
    330n farads is the capactiance.
    .330u is the same as 330n
    250V max -40 to 85 temperature range. All the other circled bitties are the various standards the cap meets.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Just to confuse you a bit more about capacitor values:
    uF (micro Farads) is the suffix used for most aluminum electrolytic capacitors. Some old capacitors you might find marked as mF are actually uF.
    1uF = 1/1,000,000 Farad, or 1.0E-6 Faraqd.
    1uF = 1,000nF. Conversely, 1nF = 0.001uF, or 1.0E-9 Farads.
    1nF = 1,000pF. Conversely, 1pF = 0.001nF, or 0.000,001uF or 1.0E-12 Farads.

    Clear as mud?
     
  8. Chrisoborski

    Thread Starter Member

    Oct 12, 2009
    25
    0
    Well I'm new but i've been tinkering with electronics for at least 4 years i think maybe more. Went to school for auto mechanics, learned some electricity there. I feel comfortable for the most part around 120 AC.

    Here's an LED Based Bulb that runs on AC. I came up with the idea on how to construct it... it uses plexi glass sheet upper and lower, PVC Main tube and a longer skinnier 2 Inch PVC. I used Epoxy, two Diodes for just in case, a bunch of blue/white LED's, and flat white paint. I used this page as a basic formula for Circuit design/ resistor values. http://www.dansdata.com/caselight.htm

    I had it plugged in for about a year and i decided i was going to increase the output since designing it i wanted it to be a low output. It was pretty low and i was going to bring it up some more but i ended up breaking half of the down tube off and popping out a LED. Then its been sitting in my drawer getting banged aorund. So this is what's left.... Ohh for a screw in socket i used one of those screw bulb base's to plug adapter that i cut open and epoxied to the PVC 2 inch...


    [​IMG]
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    Last edited: Sep 18, 2010
  9. Chrisoborski

    Thread Starter Member

    Oct 12, 2009
    25
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    Here's the Rest...

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  10. Chrisoborski

    Thread Starter Member

    Oct 12, 2009
    25
    0
    I think i got it. i can remember it by thinking, For nanofarads it would equal a percetage of a Microfarad. Like there are 3 digits including the 1 places OVER from the decimal for 1000 nanofarads to microfarads. .001uf equals 1000 nanofarads. That might sound more confusing but i can remember it visually in my head instead of thinking it out. I just have to remember that it goes in the order of Microfarads, Nanofarads , to Picofarads going to a lower order.

    It goes in the order of Microfarads , Nanofarads, then smallest is Picofarads? I think thats correct.

    Thanks
     
  11. sceadwian

    New Member

    Jun 1, 2009
    499
    37
    You should get the idea of m for micro farrads out of your head, as it according to standard notation should be milifarads which you'll be hard pressed to find on any cap, as for some reason they'll tend to use a 1000u notation, values above that tend to be listed as decimal notation of whole farrads, probably because at that boundry the general size of the device allows plain text to be used and using the m notation on large value caps might confuse industral folk.. into thinking the have a microfarrad rating and are useable in those circumstance (fire ensues)
     
  12. Chrisoborski

    Thread Starter Member

    Oct 12, 2009
    25
    0
    Now i'm really confused. Well i know that Micro farads is uF. I thought that millifarads isn't used in practice anymore. Can you explain. Where is Millifarads in respect to a farad. Is it 1,000,000 or a million Micro farads to one Farad as you are indicating. I mean i know MFD, "Micro farads",and uf equal the same thing. :confused:
     
  13. sceadwian

    New Member

    Jun 1, 2009
    499
    37
    Chris, you need to correct this notation pronto it'll confuse you madly in the end.

    Mili's notation is m
    micro's notation is u, which isn't actually a lower case u, it's the greek lower case Mu, http://en.wikipedia.org/wiki/Mu_%28letter%29

    Yes I know the upper case symbol for the lower case micro symbol happens to be M, VERY confusing, standard scientific notation for a capital M is actually MEG, which makes it even worse because Meg is notation for 10^6 not 10^-3

    Luckily this is all standardize in
    http://en.wikipedia.org/wiki/International_System_of_Units
    Under the units and prefix section you'll find the scientifically acknowledged standards symbols used.


    The notation on some caps of m farrads instead of micro (u) farads is still used, but only because it was adopted before the standards existed and the engineers have refused to let it go. You'll tend to find the old notation on non polarized power caps for power correction or motor run capacitors.
     
    Last edited: Sep 19, 2010
  14. Chrisoborski

    Thread Starter Member

    Oct 12, 2009
    25
    0
    Wow i think my brain stop working temporarily when i read your post because some how it didn't occur to me that you meant there was two different symbols. I see what you mean now, two different symbols and they can get confused.

    Geez how did that not make sense. I read the links and i see how it could be mixed up. I always new what a uF microfarad was cause they're so common.

    Wern't uF caps labeled MFD though? I think that what you were trying to get me to realize to not use M with uF. :D

    Thanks i'm glad someone was paying attention!
     
  15. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    At the time the MFD was used to represent microfarads, a 1 farad capacitor would have filled a room. At least that's what our instructors told us. Of course that was almost 50 years ago. Now, a person has to be very careful to not use the old terminology or they may end up with the wrong component.
     
  16. sceadwian

    New Member

    Jun 1, 2009
    499
    37
    At the time? I still see caps in floating around that have MFD values listed on them.
     
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